How to implement Notifications and Backend for mobile application?

Question

iOS

Good day to all! As an inexperienced developer, I need advice from already knowledgeable and skilled iOS dev representatives.
I am making an application now and there was a problem with the backend. Decided to choose for cloud data storage - Firebase. Yes, I heard a lot of negative things about him because of the lack of flexibility and compromises in everything and everything, but I decided to dwell on it, because. this is the fastest option in terms of implementation.
Note: I’m practically not familiar with the frontend and backend anymore, I don’t know how to Java and I’m generally a bum, only-Swift coder, hipster and other crap of modern dev.
So, with the preservation and correct display of data in theory, problems should not arise. But here, with regards to Notifications, everything is very blurry and unclear. In the project, I will need notifications on the conditions and I could not dig up anything on the Internet.
Let me explain with an example:
For example, I have various entrepreneurs who have different work profiles, someone is a mechanic, someone is a plumber, someone is an electrician. All of them are from different cities - someone from London, someone from Vancouver, someone from Bobruisk. And I have ordinary users who order various services. And so, some user submits a general application for the fact that he needs an electrician, and this user is located in Bobruisk. And when the user has submitted an application, all electrical entrepreneurs from Bobruisk should receive a notification that an order has appeared, write to the user and agree on the conditions. These notifications should come even when the application is turned off.
Also, in the future, an Android version will be added to the iOS app. And later there will be a site that will use this data.
And now I have no idea how this can be correctly implemented. Can anyone recommend something specific? Is it realistic to do this on Firebase? If so, how? If not, what are the equivalents? Or, if you write the server yourself, how and what is needed for this?
Immediately I apologize for my stupidity, I'm still too green in this matter. Give the young and stupid a chance.

Answer 1

Why didn't you like this option: https://firebase.google.com/docs/cloud-messaging/